From patchwork Mon Jan 25 11:44:57 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 60354 Delivered-To: patch@linaro.org Received: by 10.112.130.2 with SMTP id oa2csp1303814lbb; Mon, 25 Jan 2016 03:55:31 -0800 (PST) X-Received: by 10.66.162.164 with SMTP id yb4mr25255900pab.94.1453722931092; Mon, 25 Jan 2016 03:55:31 -0800 (PST) Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id rm12si19891621pab.225.2016.01.25.03.55.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Jan 2016 03:55:31 -0800 (PST) Received-SPF: pass (google.com: domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) client-ip=2001:1868:205::9; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) smtp.mailfrom=linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aNfis-0005j0-Lr; Mon, 25 Jan 2016 11:54:18 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aNfbR-0006JU-VR for linux-arm-kernel@lists.infradead.org; Mon, 25 Jan 2016 11:46:40 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8FC205D0; Mon, 25 Jan 2016 03:45:37 -0800 (PST) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 757B23F246; Mon, 25 Jan 2016 03:46:16 -0800 (PST) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com Subject: [PATCHv3 03/18] arm64: mm: place empty_zero_page in bss Date: Mon, 25 Jan 2016 11:44:57 +0000 Message-Id: <1453722312-23076-4-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1453722312-23076-1-git-send-email-mark.rutland@arm.com> References: <1453722312-23076-1-git-send-email-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160125_034638_288623_F96AC2CE X-CRM114-Status: GOOD ( 14.97 ) X-Spam-Score: -6.9 (------) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-6.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.101.70 listed in list.dnswl.org] -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, lorenzo.pieralisi@arm.com, arnd@arndb.de, ard.biesheuvel@linaro.org, will.deacon@arm.com, jeremy.linton@arm.com, ryabinin.a.a@gmail.com, labbott@fedoraproject.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Currently the zero page is set up in paging_init, and thus we cannot use the zero page earlier. We use the zero page as a reserved TTBR value from which no TLB entries may be allocated (e.g. when uninstalling the idmap). To enable such usage earlier (as may be required for invasive changes to the kernel page tables), and to minimise the time that the idmap is active, we need to be able to use the zero page before paging_init. This patch follows the example set by x86, by allocating the zero page at compile time, in .bss. This means that the zero page itself is available immediately upon entry to start_kernel (as we zero .bss before this), and also means that the zero page takes up no space in the raw Image binary. The associated struct page is allocated in bootmem_init, and remains unavailable until this time. Outside of arch code, the only users of empty_zero_page assume that the empty_zero_page symbol refers to the zeroed memory itself, and that ZERO_PAGE(x) must be used to acquire the associated struct page, following the example of x86. This patch also brings arm64 inline with these assumptions. Signed-off-by: Mark Rutland Reviewed-by: Catalin Marinas Tested-by: Ard Biesheuvel Reviewed-by: Ard Biesheuvel Cc: Jeremy Linton Cc: Laura Abbott Cc: Will Deacon --- arch/arm64/include/asm/mmu_context.h | 2 +- arch/arm64/include/asm/pgtable.h | 4 ++-- arch/arm64/kernel/head.S | 1 + arch/arm64/mm/mmu.c | 9 +-------- 4 files changed, 5 insertions(+), 11 deletions(-) -- 1.9.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index 2416578..600eacb 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -48,7 +48,7 @@ static inline void contextidr_thread_switch(struct task_struct *next) */ static inline void cpu_set_reserved_ttbr0(void) { - unsigned long ttbr = page_to_phys(empty_zero_page); + unsigned long ttbr = virt_to_phys(empty_zero_page); asm( " msr ttbr0_el1, %0 // set TTBR0\n" diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 2d545d7a..ccf3c48 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -121,8 +121,8 @@ extern void __pgd_error(const char *file, int line, unsigned long val); * ZERO_PAGE is a global shared page that is always zero: used * for zero-mapped memory areas etc.. */ -extern struct page *empty_zero_page; -#define ZERO_PAGE(vaddr) (empty_zero_page) +extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; +#define ZERO_PAGE(vaddr) virt_to_page(empty_zero_page) #define pte_ERROR(pte) __pte_error(__FILE__, __LINE__, pte_val(pte)) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index ffe9c2b..51370f8 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -421,6 +421,7 @@ __mmap_switched: adr_l x2, __bss_stop sub x2, x2, x0 bl __pi_memset + dsb ishst // Make zero page visible to PTW adr_l sp, initial_sp, x4 mov x4, sp diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index b25d5cb..cdbf055 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -49,7 +49,7 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS); * Empty_zero_page is a special page that is used for zero-initialized data * and COW. */ -struct page *empty_zero_page; +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, @@ -459,18 +459,11 @@ void fixup_init(void) */ void __init paging_init(void) { - void *zero_page; - map_mem(); fixup_executable(); - /* allocate the zero page. */ - zero_page = early_pgtable_alloc(); - bootmem_init(); - empty_zero_page = virt_to_page(zero_page); - /* * TTBR0 is only used for the identity mapping at this stage. Make it * point to zero page to avoid speculatively fetching new entries.